This invention relates to electrical connectors, and more particular to electrical connectors for coupling circuits on printed circuit boards.
Many computing devices, such as desktop computers, workstations, mainframe and super-computers employ multiple printed circuit boards (xe2x80x9cPCBxe2x80x9d) that include various microprocessors, printed circuits and other components that must be electrically coupled together to transmit data and/or power. The electrical traces on one or more layers of the PCB form the printed circuits and typically terminate in one or more terminals or contacts for making connections. Ever decreasing element sizes, such a pitch (i.e., the spacing between successive components), width, and height, exacerbate the problem of providing secure and reliable connections between the printed circuits. Precise positioning on the order of thousandths of an inch is often necessary. Consistent pressure across each of the many contacts is also desirable to assure a reliable connection. A single failed or intermittent connection can result in large amounts of xe2x80x9cdown-timexe2x80x9d for the computing device, and costly troubleshooting by highly skilled technicians.
Flexible circuit substrates provide low resistance, low impedance connections. Such connections are particularly desirable in parallel processing systems, where the timing of signals is critical. Flexible circuit substrates consist of a number of electrical traces on a small number of layers (e.g., approximately 2-8) of printed circuit board material (e.g., FR-4 epoxy-fiberglass laminate). The resulting substrate is highly flexible, hence convenient for making connections in tight spaces and/or at an angle. However, because of their flexibility, such connectors present a challenge in providing even contact pressure across all contacts.
Highly parallel processing super-computers present a particularly significant problem in terms of space constraints. These computers rely on a high number of connections between circuit boards that each carry one or more microprocessors. The nature of parallel processing places high demands on the timing of signals, including clock signals across the various computer components. The PCBs are spaced relatively close together to reduce the length of the connections between the PCBs in an effort to improve the timing of the signals. The tight spacing hinders the ability of technicians to access particular computer components, such as the PCBs and electrical connectors. This presents a particular problem to computer manufacturers and owners who desire a modular design that permits failed components to be quickly and easily replaced. If serviceable, a modular design would also permit the addition of new or additional processors as desired, for example when more processing power is required or when the processors become more affordable. This could significantly extend the life of the computing device.
A reliable, precise, and highly manipulable electrical connector is required to couple printed circuits between printed circuit boards. Additionally the connection should be secure over a time period commensurate with the expected life of the computing device to avoid costly maintenance and should allow easy replacement and/or addition of various computer components such as PCBs.
Under one aspect of the invention, resilient pressure pads carried by opposed clamping members of an electrical connector bias flexible circuit substrates to a circuit board. Respective wells in the clamping members receive the pressure pads and provide support to a side wall of the pressure pads. Frames carried by the clamping members provide additional support to the side walls of the pressure pads.
Under another aspect of the invention, the pressure pads include a raised edge along a periphery of a contact surface of the pressure pad. Additionally, or alternatively, a support shoulder in the well cooperates with a recess along a periphery of a mounting surface of the pressure pad opposed to the contact surface.
Under another aspect of the invention, the pressure pads include a resilient pressure pad core having a first durometer value and a resilient pressure pad sleeve having a second duormeter value greater than the first durometer value.
Under a further aspect of the invention, alignment structure on the frame cooperate with alignment structure on the clamping members, the printed circuit boards and the flexible circuit substrates to align contacts on the flexible circuit substrates with contacts on the printed circuit boards, and to further align the pressure pads with the contacts.